The present invention concerns a method and apparatus for making photographic prints on stock from negatives that differ in density range.
The negatives that photographic prints are made from often have very different ranges of density, meaning that the difference between the darkest point and the lightest point of the negative can be either very great or very small. Since the contrast or "exposure gradient" of the photographic stock--that is, the slope of the photographic density curve--is related over a specific range of densities to a mean negative density range, it is impossible to make really satisfactory prints from negatives with densities at either extreme. Negatives with a narrow range of densities, very underexposed for example, will result in very flat prints. Ordinary stock will also not correctly represent the difference in density characteristic of negatives with a very wide density range; for example, overexposed, flash, or back-lit negatives. There has accordingly been a need to adapt the gradient of the stock to the type of negative.
Two methods of controlling the gradient when printing from black-and-white negatives have been known for some time. The first uses a very harsh stock subjected to lower-threshold preliminary illumination. The second employs a special type of stock with two coatings of different gradient, one sensitive to blue and the other to yellow, and adjusts the harshness of the stock by subjecting it to specific proportions of blue and yellow light. These approaches, which are disclosed in the U.S. Pat. No. 3,753,707, cannot be employed to make color prints.
One contemporary method constitutes unsharp masking of the printing light with an LCD matrix actuated point-by-point by a computer. When the negative has a wide range of densities, the matrix will decrease the intensity of the printing light in the lightest areas, confining the range to the capacities of the stock. However, this method, which is disclosed in the U.S. Pat. No. 4,239,385, is relatively complicated.